1. Field of the Invention
The present invention relates to the field of temperature measurements and can be employed in various temperature measuring devices utilizing semiconductor and/or ceramic thermistors with positive and/or negative temperature coefficients.
2. Discussion of the Background Art
Available thermistor probes consist of ceramic thermistors with leads that are covered by a metal or plastic tube having a diameter in the range of (4–7) mm and a length of up to 30 cm. The tube is placed in an area in which temperature is to be measured, and the thermistor inside of the tube measures temperature outside of the tube with some delay in time due to a temperature gradient between a real environment temperature and the thermistor temperature inside the tube. The internal volume of the tube is large enough to accommodate a ceramic thermistor, with two wires, encapsulated in epoxy or glass. The tube separates the thermistor from an environment outside of the tube. The main purpose of placing a ceramic thermistor inside of the tube is to prevent direct contact with a potentially hostile surrounding environment since ceramic thermistors easily absorb water vapor that adversely affects the thermistor performance. Such thermistor probes have a number of disadvantages.
In prior art thermistor probes, the thermistor body is isolated inside a metal tubing far enough from the point of temperature measurement to create a temperature gradient between thermistor and media outside the tube. The probes are also not designed for monitoring temperature at multiple points with two or more thermistors. Furthermore, it is impossible to use such probes for temperature measurements in the presence of microwave radiation because of intensive RF absorption by the massive metal tube and metal wires. It is nearly impossible to use these probes to measure temperature at locations that are hard to reach. Finally, the production cost of such thermistor probes is relatively high.